The Measured Impact of Chromatic Atmospheric Effects on Barycentric Corrections: Results from the EXtreme PREcision Spectrograph. (arXiv:1906.01653v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Blackman_R/0/1/0/all/0/1">Ryan Blackman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ong_J/0/1/0/all/0/1">Joel Ong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fischer_D/0/1/0/all/0/1">Debra Fischer</a>

One source of error in high-precision radial velocity measurements of
exoplanet host stars is chromatic change in Earth’s atmospheric transmission
during observations. Mitigation of this error requires that the photon-weighted
barycentric correction be applied as a function of wavelength across the
stellar spectrum. We have designed a system for chromatic photon-weighted
barycentric corrections with the EXtreme PREcision Spectrograph (EXPRES) and
present results from the first year of operations, based on radial velocity
measurements of more than $10^3$ high-resolution stellar spectra. For
observation times longer than 250 seconds, we find that if the chromatic
component of the barycentric corrections is ignored, a range of radial velocity
errors up to 1 m s$^{-1}$ can be incurred with cross-correlation, depending on
the nightly atmospheric conditions. For this distribution of errors, the
standard deviation is 8.4 cm s$^{-1}$ for G-type stars, 8.5 cm s$^{-1}$ for
K-type stars, and 2.1 cm s$^{-1}$ for M-type stars. This error is reduced to
well-below the instrumental and photon-noise limited floor by frequent flux
sampling of the observed star with a low-resolution exposure meter
spectrograph.

One source of error in high-precision radial velocity measurements of
exoplanet host stars is chromatic change in Earth’s atmospheric transmission
during observations. Mitigation of this error requires that the photon-weighted
barycentric correction be applied as a function of wavelength across the
stellar spectrum. We have designed a system for chromatic photon-weighted
barycentric corrections with the EXtreme PREcision Spectrograph (EXPRES) and
present results from the first year of operations, based on radial velocity
measurements of more than $10^3$ high-resolution stellar spectra. For
observation times longer than 250 seconds, we find that if the chromatic
component of the barycentric corrections is ignored, a range of radial velocity
errors up to 1 m s$^{-1}$ can be incurred with cross-correlation, depending on
the nightly atmospheric conditions. For this distribution of errors, the
standard deviation is 8.4 cm s$^{-1}$ for G-type stars, 8.5 cm s$^{-1}$ for
K-type stars, and 2.1 cm s$^{-1}$ for M-type stars. This error is reduced to
well-below the instrumental and photon-noise limited floor by frequent flux
sampling of the observed star with a low-resolution exposure meter
spectrograph.

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